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Pure alumina is obtained from bauxite - Leaving Cert Chemistry - Question B - 2018
Question B
Pure alumina is obtained from bauxite. The first of three chemical reactions in this process is the reaction between the alumina in the bauxite and sodium hydroxide ... show full transcript
Worked Solution & Example Answer:Pure alumina is obtained from bauxite - Leaving Cert Chemistry - Question B - 2018
Step 1
Write balanced equations to describe the last two stages of this process.
Answer
To describe the last two stages of the aluminum extraction process:
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First, the soluble sodium aluminate (NaAlO2) formed reacts with water and sodium hydroxide:
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Next, the aluminum hydroxide precipitates and is then calcined to give pure alumina (Al2O3):
These equations illustrate the conversion from sodium aluminate back to aluminum hydroxide, and finally to pure alumina.
Step 2
How is the pure alumina then converted into aluminium metal?
Answer
The conversion of pure alumina into aluminum metal involves the electrolysis of molten alumina using an electrolytic cell. The process is as follows:
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The alumina (Al2O3) is dissolved in molten cryolite (Na3AlF6), which lowers the melting point and enhances conductivity.
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At the cathode, aluminum ions are reduced:
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At the anode, oxide ions are oxidized back to oxygen:
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The process requires regular replacement of carbon electrodes as they are consumed in this electrochemical reaction.
Step 3
How does the aluminium industry produce aluminium from alumina economically while addressing climate change concerns?
Answer
The aluminum industry employs several strategies to produce aluminum economically while addressing climate change concerns:
- Renewable Energy Sources: Many aluminum producers are transitioning to renewable energy sources such as hydroelectric power, which significantly reduces the carbon footprint compared to conventional fossil fuels.
- Use of Cryolite: The use of cryolite in the electrolysis process helps to reduce energy requirements and improve efficiency.
- Recycling: The industry emphasizes recycling aluminum, which requires only about 5% of the energy needed to produce new aluminum from ore, further mitigating environmental impacts.